git/diffcore-pickaxe.c, branch gitk-resize-error

xdiff-interface: replace discard_hunk_line() with a flag

2021-05-11T03:47:31Z

Remove the dummy discard_hunk_line() function added in 3b40a090fd4 (diff: avoid generating unused hunk header lines, 2018-11-02) in favor of having a new XDL_EMIT_NO_HUNK_HDR flag, for use along with the two existing and similar XDL_EMIT_* flags. Unlike the recently amended xdiff_emit_line_fn interface which'll be called in a loop in xdl_emit_diff(), the hunk header is only emitted once. It makes more sense to pass this as a flag than provide a dummy callback because that function may be able to skip doing certain work if it knows the caller is doing nothing with the hunk header. It would be possible to do so in the case of -U0 now, but the benefit of doing so is so small that I haven't bothered. But this leaves the door open to that, and more importantly makes the API use more intuitive. The reason we're putting a flag in the gap between 1<<0 and 1<<2 is that the old 1<<1 flag was removed in 907681e940d (xdiff: drop XDL_EMIT_COMMON, 2016-02-23) without re-ordering the remaining flags. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe -G: don't special-case create/delete

2021-05-11T03:47:31Z

Instead of special-casing creations and deletions let's just generate a diff for them. This logic of not running a diff under -G if we don't have both sides dates back to the original implementation of -S in 52e9578985f ([PATCH] Introducing software archaeologist's tool "pickaxe"., 2005-05-21). In the case of -S we were not working with the xdiff interface and needed to do this, but when -G was implemented in f506b8e8b5f (git log/diff: add -G that greps in the patch text, 2010-08-23) this logic was diligently copied over. But as the performance test added earlier in this series shows, this does not make much of a difference. With: time GIT_TEST_LONG= GIT_PERF_REPEAT_COUNT=10 GIT_PERF_MAKE_OPTS='-j8 CFLAGS=-O3' ./run origin/next HEAD~ HEAD -- p4209-pickaxe.sh With the HEAD~ commit being the preceding "pickaxe -G: terminate early on matching lines" we get these results. Note that it's only the -G codepaths that are relevant to this change: Test origin/next HEAD~ HEAD ----------------------------------------------------------------------------------------------------------------------------------------- 4209.1: git log -S'int main' .. 0.35(0.32+0.03) 0.35(0.33+0.02) +0.0% 0.35(0.30+0.05) +0.0% 4209.2: git log -S'æ' .. 0.46(0.42+0.04) 0.46(0.41+0.05) +0.0% 0.46(0.42+0.04) +0.0% 4209.3: git log --pickaxe-regex -S'(int|void|null)' .. 0.65(0.62+0.02) 0.64(0.61+0.02) -1.5% 0.64(0.60+0.04) -1.5% 4209.4: git log --pickaxe-regex -S'if *\([^ ]+ & ' .. 0.52(0.45+0.06) 0.52(0.50+0.01) +0.0% 0.54(0.47+0.04) +3.8% 4209.5: git log --pickaxe-regex -S'[àáâãäåæñøùúûüýþ]' .. 0.39(0.34+0.05) 0.39(0.34+0.04) +0.0% 0.39(0.36+0.03) +0.0% 4209.6: git log -G'(int|void|null)' .. 0.60(0.55+0.04) 0.58(0.54+0.03) -3.3% 0.58(0.49+0.08) -3.3% 4209.7: git log -G'if *\([^ ]+ & ' .. 0.61(0.52+0.06) 0.59(0.53+0.05) -3.3% 0.59(0.54+0.05) -3.3% 4209.8: git log -G'[àáâãäåæñøùúûüýþ]' .. 0.61(0.51+0.07) 0.58(0.54+0.04) -4.9% 0.57(0.51+0.06) -6.6% 4209.9: git log -i -S'int main' .. 0.36(0.31+0.04) 0.36(0.34+0.02) +0.0% 0.35(0.32+0.03) -2.8% 4209.10: git log -i -S'æ' .. 0.36(0.33+0.03) 0.39(0.34+0.01) +8.3% 0.36(0.32+0.03) +0.0% 4209.11: git log -i --pickaxe-regex -S'(int|void|null)' .. 0.83(0.77+0.05) 0.82(0.77+0.05) -1.2% 0.80(0.75+0.04) -3.6% 4209.12: git log -i --pickaxe-regex -S'if *\([^ ]+ & ' .. 0.67(0.61+0.03) 0.64(0.61+0.03) -4.5% 0.63(0.61+0.02) -6.0% 4209.13: git log -i --pickaxe-regex -S'[àáâãäåæñøùúûüýþ]' .. 0.40(0.37+0.02) 0.40(0.37+0.03) +0.0% 0.40(0.36+0.04) +0.0% 4209.14: git log -i -G'(int|void|null)' .. 0.58(0.51+0.07) 0.59(0.52+0.06) +1.7% 0.58(0.52+0.05) +0.0% 4209.15: git log -i -G'if *\([^ ]+ & ' .. 0.60(0.54+0.05) 0.60(0.54+0.06) +0.0% 0.60(0.56+0.03) +0.0% 4209.16: git log -i -G'[àáâãäåæñøùúûüýþ]' .. 0.58(0.51+0.06) 0.57(0.52+0.05) -1.7% 0.60(0.48+0.09) +3.4% This small simplification really doesn't buy us much now, but I've got plans to both convert the pickaxe code to using a PCREv2 backend[1] and to implement additional pickaxe modes to do custom searches through the diff[2]. Always having the diff available under -G is going to help to simplify both of those changes. 1. https://lore.kernel.org/git/20210203032811.14979-22-avarab@gmail.com/ 2. https://lore.kernel.org/git/20190424152215.16251-3-avarab@gmail.com/ Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe -G: terminate early on matching lines

2021-05-11T03:47:31Z

Solve a long-standing item for "git log -Grx" of us e.g. finding "+ str" in the diff context and noting that we had a "hit", but xdiff diligently continuing to generate and spew the rest of the diff at us. This makes use of a new "early return" xdiff interface added by preceding commits. The TODO item (or, the NEEDSWORK comment) has been there since "git log -G" was implemented. See f506b8e8b5f (git log/diff: add -G that greps in the patch text, 2010-08-23). But now with the support added in the preceding changes to the xdiff-interface we can return early. Let's assert the behavior of that new early-return xdiff-interface by having a BUG() call here to die if it ever starts handing us needless work again. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

xdiff-interface: prepare for allowing early return

2021-05-11T03:47:31Z

Change the function prototype of xdiff_emit_line_fn to return an "int" instead of "void". Change all of those functions to "return 0", nothing checks those return values yet, and no behavior is being changed. In subsequent commits the interface will be changed to allow early return via this new return value. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe -S: slightly optimize contains()

2021-05-11T03:47:31Z

When the "log -S" switch counts occurrences of on the pre-image and post-image of a change. As soon as we know we had e.g. 1 before and 2 now we can stop, we don't need to keep counting past 2. With this change a diff between A and B may have different performance characteristics than between B and A. That's OK in this case, since we'll emit the same output, and the effect is to make one of them better. I'm picking a check of "one" first on the assumption that it's a more common case to have files grow over time than not. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe: rename variables in has_changes() for brevity

2021-05-11T03:47:31Z

Rename the {one,two}_contains variables to c{1,2}. This will make a follow-up change easier to read. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe -S: support content with NULs under --pickaxe-regex

2021-05-11T03:47:31Z

Fix a bug in the matching routine powering -S --pickaxe-regex so that we won't abort early on content that has NULs in it. We've had a hard requirement on REG_STARTEND since 2f8952250a8 (regex: add regexec_buf() that can work on a non NUL-terminated string, 2016-09-21), but this sanity check dates back to d01d8c67828 (Support for pickaxe matching regular expressions, 2006-03-29). It wasn't needed anymore, and as the now-passing test shows, actively getting in our way. Since we always require REG_STARTEND support we do not need to stop at NULs. If we are dealing with a haystack with NUL in it. The needle may be behind that NUL. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe: assert that we must have a needle under -G or -S

2021-05-11T03:47:31Z

Assert early in diffcore_pickaxe() that we've got a needle to work with under -G and -S. This code is redundant to the check -G and -S get from parse-options.c's get_arg(), which I'm adding a test for. This check dates back to e1b161161d (diffcore-pickaxe: fix infinite loop on zero-length needle, 2007-01-25) when "git log -S" could send this code into an infinite loop. It was then later refactored in 8fa4b09fb1 (pickaxe: hoist empty needle check, 2012-10-28) into its current form, but it seemingly wasn't noticed that in the meantime a move to the parse-options.c API in dea007fb4c (diff: parse separate options like -S foo, 2010-08-05) had made it redundant. Let's retain some of the paranoia here with a BUG(), but there's no need to be checking this in the pickaxe_match() inner loop. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe: refactor function selection in diffcore-pickaxe()

2021-05-11T03:47:31Z

It's hard to read this codepath at a glance and reason about exactly what combination of -G and -S will compile either regexes or kwset, and whether we'll then dispatch to "diff_grep" or "has_changes". Then in the "--find-object" case we aren't using the callback function, but were previously passing down "has_changes". Refactor this code to exhaustively check "opts", it's now more obvious what callback function (or none) we want under what mode. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

pickaxe/style: consolidate declarations and assignments

2021-05-11T03:47:31Z

Refactor contains() to do its assignments at the same time that it does its declarations. This code could have been refactored in ef90ab66e8e (pickaxe: use textconv for -S counting, 2012-10-28) when a function call between the declarations and assignments was removed. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano